Each year numerous automobile accidents are caused by vehicle driver distractions. The National Highway Traffic Safety Administration (NHTSA) estimates that driver distraction is directly involved in twenty to thirty percent of all automobile accidents or roughly 1.6 million automobile accidents in the U.S. annually. Visual distraction of the driver is attributed to many of the accidents. For this reason, there has been interest in developing a driver monitoring system for determining if the driver is paying attention to the forward field-of-view. This information can be used to issue an alert if the driver's attention is directed away from the road too long or too often, and possibly to belay other warnings (such as collision-avoidance warnings) if the driver is paying attention to the forward field-of-view. An example of such a monitoring system is Delphi Automotive's Driver State Monitor, which processes a video image of a driver's face to characterize the driver's eye gaze direction (on-road vs. off-road), and to issue an alert if the proportion of off-road eye gaze over a specified period of time exceeds a threshold. However, video processing typically requires high-speed signal processing capabilities, and detection of the driver's eyes can be hampered by various kinds of obstructions (including sunglasses) disposed between the video imager(s) and the driver's face. Accordingly, what is needed is a more reliable and cost-effective way of assessing driver distraction.